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Is More Protein Always Better? Despite the Craze Around the Nutrient, Research-Backed Evidence About Its Benefits Is Complicated
It can be difficult to see through the array of flashy, protein-packed products and determine whether you need more of it—and which foods to consume to get it. We asked health experts about the benefits and drawbacks of chasing protein
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Protein is in practically everything these days. Brightly colored lettering advertises that extra helpings have been added to pancake mixes, popcorn bags and even Starbucks drinks. Health and fitness influencers share tips on social media to ensure that their audiences are consuming as much of the nutrient as possible.
But is more protein better? That depends—on your goals, your health and your protein sources.
Some people, like those doing intense workouts to build muscles, will probably benefit from extra protein. But the average couch potato might not, especially if they’re trying to boost their intake with junk foods like protein-enhanced Pop-Tarts.
“It doesn’t make it any better because you add protein to the package,” says Daphene Altema-Johnson, a dietician at the Johns Hopkins Center for a Livable Future. “People think it’s healthier—it’s not. A cookie is a cookie; a pastry is a pastry.” The same goes for loading your diet with protein from animal products, since high meat consumption has been linked to health problems, including cancer.
Still, you probably won’t suffer any detrimental health effects from additional protein alone. Some people, such as senior citizens, have even been advised to eat more of it for health reasons. On the other hand, a growing body of research—mostly in animals—hints that restricting intake of the nutrient can promote healthy aging.
Conflicting health advice and shifting dietary guidelines can make a conscious eater feel a sense of whiplash. So, how much protein do you really need, and why is it so difficult to figure it out? Smithsonian magazine talked to several health experts about the complications of nutrition research.
The building blocks
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Protein is an important part of the human diet. You need to eat a relatively large amount of it for your body to function properly. That’s why protein is considered a macronutrient, along with carbohydrates and fats. The World Health Organization (WHO) recommends that protein make up 10 to 15 percent of an adult’s daily calorie intake, while fats make up 15 to 30 percent and carbohydrates make up 45 to 75 percent.
Your body breaks down the protein that you eat into its building blocks: amino acids. Humans rely on 20 types of these molecules, but nine of them can only be obtained from food—those are called “essential” amino acids. The body rearranges these ingredients to construct new proteins, which are crucial for pretty much every bodily function.
“They do more than just make muscle,” says Teresa Fung, a nutritional epidemiologist at Simmons University and the Harvard T.H. Chan School of Public Health. Many hormones are proteins. Our organs contain proteins. Infection-fighting antibodies are proteins. All enzymes, which help us digest food and play various biochemical functions in the body, are proteins, she notes.
Because protein is so vital, the United States introduced in the early 1940s a recommended dietary allowance for the nutrient, set as a “guide for planning adequate nutrition” amid food shortages during World War II. By the late 1980s, the guidance suggested that the average adult consume around 0.8 grams of protein per kilogram of body weight each day, which equals about 54 grams for a person who weighs 150 pounds.
The benchmark has been widely used as a guideline by health professionals ever since. It closely mirrors the WHO’s current daily recommendation, which is 0.83 grams of protein per kilogram of body weight.
This year, however, the U.S. guidance got an update. As of January 2026, the federal dietary guideline suggests a daily protein intake goal of 1.2 to 1.6 grams per kilogram of body weight, which would put a 150-pound person at about 82 to 109 grams of protein per day.
“I think it was a very good decision,” says David Allison, chief of the nutrition division and director of the Children’s Nutrition Research Center, operated by Baylor College of Medicine, the Texas Children’s Hospital and the U.S. Department of Agriculture’s Agricultural Research Service. “I would have probably made the same approximate decision.”
Exercise physiologist Stuart Phillips agrees with that range, too, although he says that protein intake should come second to ensuring you’re getting an adequate amount of physical activity. “Exercise bakes the cake, but protein adds a thin layer of icing on top,” says Phillips, of McMaster University in Canada.
Too much or too little?
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The new guideline doesn’t necessarily mean you need to start searching for protein-packed products. Most Americans are already eating within the updated recommended range, Altema-Johnson says, so there’s likely no need to up your intake of the nutrient unless you have specific fitness goals or a health reason, like to preserve muscle in old age or aid recovery from surgery.
Even athletes doing the most aggressive training to build muscles tend to stop seeing huge benefits beyond 1.6 grams of protein per kilogram of body weight, Phillips says. “The last few tiny little drops might come out at intakes that are greater than 1.6, but most mere mortals don’t really worry about that sort of thing.” (Bodybuilders are a different story, he notes.)
That said, your body can only use so much protein at a time. “We really do not have a protein store that we can just stash away,” Fung says. Amino acids that can’t be used get turned into energy in the form of calories. However, that “should be at the bottom of [protein’s] job description,” because you can also get calories from carbohydrates and fats, while bodily proteins like enzymes can only be made from dietary protein, she adds.
Nevertheless, “eating more is not a problem, because the excess protein can usually be handled by a healthy kidney and a healthy liver,” Fung says. People who have issues with those organs, or rare diseases that affect amino acid processing, typically work with health professionals to build a diet with limited protein.
Even more broadly, however, eating less protein may be emerging as a health strategy of its own. Over the past two decades, evidence that restricting dietary protein can promote healthy aging has been mounting. A literature review published last month in the journal Cell Press Blue highlights several studies in which rodents, flies and other creatures that were fed low-protein diets lived longer than their counterparts that ate higher levels of protein.
“You can see it” in protein-restricted lab rodents, which have shinier coats and act livelier than control animals, says Cristal Hill, a biologist who studies aging at the University of Southern California Leonard Davis School of Gerontology.
What’s behind those benefits in animals? One reason seems to stem from a molecule called mammalian target of rapamycin, or mTOR. Restricting protein intake appears to prevent mTOR from linking up with certain other molecules in a complex, which allows improved removal of cellular trash.
“What we want to do is allow for the cell to clean itself up,” Hill says. “If we give too many nutrients, then the cell doesn’t have time to do that. It doesn’t have time to clean up, or it doesn’t have time to rest.”
Another reason might be that limiting protein puts the liver in a stressed state, forcing it to secrete something called fibroblast growth factor 21, or FGF21, which Hill describes as an “anti-diabetic health hormone” and “longevity hormone.” Past research, mainly in animals, suggests it promotes calorie burning, reduces triglycerides in the blood and helps protect against the effects of aging.
Boosting FGF21 also seems to lead to fewer senescent, or “zombie,” cells, which generally accumulate with age and cause problems like tissue dysfunction and inflammation, says Dudley Lamming, a biologist who studies aging at the University of Wisconsin School of Medicine and Public Health and a co-author of the recent literature review.
Protein restriction also might improve the function of mitochondria, which provide energy to cells. Limiting intake of the nutrient in rodents appears to increase mitochondrial activity and reduce the organelles’ production of molecules called reactive oxygen species, which damage DNA.
Did you know? Calorie restriction
The field of protein-restriction research follows in the footsteps of calorie restriction. Scientists first reported in 1935 that reducing calorie intake in rats could extend their lives. Since then, studies in animals and some in humans have shown that limiting calories can benefit life span and health span, although there’s not enough evidence to recommend this eating strategy to the public.
In humans, protein restriction could look like eating just enough of the nutrient to hit the recommended dietary allowance. While more research will be needed to make health recommendations, experts say that whether you should choose a high- or low-protein diet might be related to how much you exercise.
“Based on our animal work,” Lamming says, “it seems that animals that are exercising can use a lot more protein and are protected from some of the negative effects of having a higher-protein diet. Whereas if they’re sedentary, then they get some of the things we observe in humans and mice that are eating higher-protein diets, which includes the accumulation of fat and the development of insulin resistance.”
That hints that “people who are sedentary or incapable of exercising might be better sticking with the [recommended dietary allowance],” Lamming adds. Moreover, “we should all be moving and exercising more.”
A messy research field
It’s important to remember that most protein restriction studies were conducted in animals, whose biology and lifestyles do not perfectly align with those of humans. What’s more, “we don’t know what it does for your quality of life. It’s hard to ask the mouse,” Allison says.
The few studies that involved people were quite short, up to around eight weeks, and mainly looked at metabolic outcomes, Lamming notes. “But there’s a lot of other outcomes that people might be concerned about with muscle, including skeletal muscle health and strength and function, as well as bone health,” which is thought to benefit from more protein.
Even among mice, the metabolic health effects of a low-protein diet vary depending on the mouse strain and the animal’s sex, according to a study published in Cell Metabolism in 2022.
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That suggests there’s “not a generic rule that then plays out from a mouse as a mammal to a human as a mammal,” Phillips says. “When we look at the human observational data,” he adds, excess protein, “at worst, is neutral.”
But conducting dietary protein studies in humans is notoriously difficult. With longer-term nutrition research, participants can sneak in other foods if they’re unhappy with what they’ve been told to eat, or they might forget what they’ve consumed when filling out a questionnaire, Lamming says.
More tightly controlled trials are generally quite short, usually on the scale of weeks or months, he adds, “because people don’t want to have their diet controlled for a really long time.” But the limited timeline also usually forces researchers to rely on proxies for health, such as markers of cholesterol or blood glucose, to make inferences about a cause and effect, Phillips notes.
Participants might also figure out which treatment group they’re in. In a clinical trial with an experimental medication, for example, participants—and often the researchers involved—do not know who is getting the new drug and who is getting the control to avoid a placebo effect in a practice called blinding.
During a short-term nutrition study, “I can give you a gel or a shake or something that might be more or less indistinguishable from another that’s different in calories or fat or protein or whatever,” Allison says. “But I can’t give you a diet like that for years at a time or even weeks at a time that’s blinded. You know if you’re eating turkey versus pasta.”
Although months- to yearslong randomized controlled trials—experiments that arbitrarily split participants into control and treatment groups—are the gold standard in clinical research, “it’s impossible to get to that level of precision” in nutrition studies, Allison adds.
A better approach to protein
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So, if you’re still aiming to raise your protein intake, what’s the best course of action? Experts who talked to Smithsonian emphasized eating plants that are rich in the nutrient.
Just a couple decades ago, the widespread view was that animal protein was superior to plant protein. That’s largely because foods like meat, eggs and dairy contain protein that’s easier to digest and more readily available to the body. In plant products like grains and beans, proteins are structured a bit differently, and the foods often have fiber or carbohydrates, among other components that can impede digestibility. But the difference is minor—it’s generally only around 10 to 20 percent tougher to digest plant protein.
Another argument has been that because animal protein has more balanced proportions of essential amino acids, people eating plant-based diets must be more mindful of the foods they eat at each meal to ensure they are getting all their protein building blocks at once.
That’s a misconception, Fung says. These different amino acids can be—and usually are—consumed throughout the day, even among vegetarians. “People don’t just eat one type of plant source,” she notes. “As long as we eat a variety of plant foods, generally, it’s not a problem.” Plant sources with a good balance of protein building blocks include quinoa, soybeans, buckwheat and chia seeds.
Increasing your protein with animal products, meanwhile, may come with some negative health effects linked to eating more meat, including an elevated risk of death and cancer. A diet high in plant proteins, on the other hand, is associated with lower mortality risk.
Plant protein measures up in muscle building, too. A study published last year in the journal Medicine & Science in Sports & Exercise found that athletic young adults who consumed vegan diets built muscle proteins at the same rate as meat eaters.
The findings track with Phillips’ real-life experience. “I work with two exceptionally good Olympic medal-winning vegan athletes,” he says. “Veganism didn’t hold them back.”
He and other experts emphasize that you should keep your distance from highly processed protein-packed items, which typically just have added protein isolated from dairy, soybeans, peas or other naturally protein-rich sources. It’s largely a marketing tactic, they say. Food companies worldwide more than quadrupled the number of high-protein products offered between 2013 and 2023, researchers reported in the journal Food Supplements and Biomaterials for Health in 2024.
Consumers should instead look at a protein source’s entire nutrient profile. For instance, protein-rich beans, legumes and whole grains are packed with something most Americans aren’t eating enough of: fiber. It’s important for gut health, managing blood sugar and cholesterol, and so much more, but animal protein sources don’t have it. Diets low in fiber and high in processed meats might even be contributing to the rising rates of colon cancer among young adults.
“People eat so much animal protein at the expense of plants,” Altema-Johnson says. She recommends adding variety to your “protein package.” By mixing it up, she adds, you are probably automatically reducing your fat intake, increasing your fiber and boosting other nutrients needed to fuel a long, healthy life.
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